Once I have the basic shape of the nose I start doing the same thing for the eyes. I start with a very basic shape made from a plane (using Cut tools) and extrude the edges the same way as I did it for the nose. Then I very quickly place a sphere in it to be sure the eyelids will wrap around the eye ball (Fig.03).

Fig.03

As I model the eye I add more definition to the lacrimal caruncle, which is the pink part on the inside of the eye (you can see this in the corner of the eye). Two things that are very important to keep in mind when modeling an eye are that the eyelids are very thick and the pink part has to follow the eye movement. A common mistake that we all make is to make the eyelid very thin when in fact they are quite thick. Even if your model is the best model ever, if the eyelids are too thin there will always be something weird about the eyes of your character. Having them thick will help the overall appearance and will give more space for the specular/reflection etc.

Once the base of my eye is done I start connecting it to the nose, while trying to keep the flow of the face muscles. For the mouth, I again start modeling it from the inside (Fig.04).

Fig.04

For the ear I do things a little differently. I start by using a plane, but instead of expanding it from the external auditory canal (hole), I instead create a rough shape for the antihelix and, as I did previously, I extrude edges by holding Shift and pushing the vertices in and out (Fig.05).

Fig.05

Since all the wrinkles and other skin marks on the face are the result of the face muscles deforming the skin, you want to have edge loops that will give you a nice topology for when you sculpt. Even if this will end up being a still picture, I still want to have a model that I could animate or apply different expressions to, and I want the edge loops to provide me with this possibility (Fig.06).